Monroe car bombing investigation at a 'sticking point,' according to authorities

View full sizeAP Photo | The Monroe Evening NewsA car burns on E. Elm Ave. near I-75 Tuesday Sept. 20, 2011 in Monroe, Mich. after it exploded as it was being driven by a man and his two sons.

Federal authorities are calling a news conference to discuss the investigation of a car bombing in Monroe nearly six months ago.

No arrests or charges will be announced Thursday in Detroit. In fact, the Bureau of Alcohol, Tobacco, Firearms and Explosives says the investigation has reached a "sticking point" and more information is needed.

Monroe lawyer Erik Chappell and two sons were injured when a bomb attached to his car exploded last September, about 35 miles southwest of Detroit. Chappell says he believes he knows who's responsible.

ATF spokesman Donald Dawkins says there are people of interest but no arrests have been made.